| 摘要 |
680,127. Gas turbine plant; centrifugal compressors. ROLLS-ROYCE, Ltd. Oct. 4. 1950 [Oct. 4, 1949], No. 25552/49. Classes 110 (i) and 110 (iii) In a gas turbine plant comprising low pressure and high pressure compressor stages connected in series and driven by mechanically independent turbines, one or more by-pass valves are connected with the interstage ducting so as to permit the flow of working medium from or into the ducting without passing through the low pressure stage, the valves being loaded in the sense of closure by a pressure derived from the high pressure stage and in the sense of opening by the pressure within the ducting. Air is compressed by a low presure stage 10, Fig. 1, and a high pressure stage 13, driven by low and high presure turbines 19 and 16 respectively and delivered to a combustion chamber 15. The combustion gases pass through the turbines 16 and 19 and, it may be, an intermediate turbine 17 driving a power output shaft 17a. An intercooler 11 and an air preheater 14 are provided. In the event of the turbine 17 overspeeding, the fuel supply to the combustion chamber 15 is reduced or shut off by a centrifugally operated trip mechanism. The resulting back-surge of the working medium contained in the combustion chamber 15 and ducting 20 causes a pressure rise in the ducting 12. To avoid exceeding the maximum permissible delivery pressure of the stage 10, the ducting 12 is vented to atmosphere through a valve 21, which is normally kept closed by the delivery pressure of stage 13, communicated to a piston 24a, Fig. 3, by way of a conduit 25. The piston may be replaced by a flexible diaphragm. To ensure operation, the valve is preferably urged towards the open position by a spring 26. Alternatively or in addition, the effective area of the valve element 22 is greater than that of the piston or diaphragm. To permit the plant to run under low power conditions with the stage 10 by-passed, the application of pressure to the piston or diaphragm may be controlled by a valve which is operated either manually or automatically at a predetermined pressure ratio of the stage 13. The spring 26 holds the valve open when the plant is stationary, and so permits the stage 10 to be by-passed when the plant is started by rotation of the shaft 16a by an external means. A separate valve may be provided for this purpose. |
